Internal arc energy in electrical equipment such as power transformers and shunt reactors is generated when insulating fluid inside a transformer tank is vaporized and an expanding gas bubble is created. The pressure increase of the expanding gas during an arc fault event can cause the tank to bulge or rupture.
In the case of tank rupture, the seams and welds of the tank separate. In the case of deformation, the tank walls may bulge. In both situations, objects and particles may be expelled forcefully over a sizeable distance causing damage to persons and property. While pressure relief devices and modification of tank dimensions have been utilized with varying degrees of success, there is room for improvement in the design of a tank for electrical equipment that is able to withstand overpressure during an arc fault and thus, resistant to rupture.